Elastomers associated with cords of radial tires at points close to and removed from beads

ABSTRACT

A radial pneumatic tire comprises at least one carcass ply formed of cords. Adjacent to the tire tread, the cords are calendered in an elastomer of a first grade and spaced apart from one another by an elastomer of a second grade. Adjacent to the tire beads, the cords are calendered in and spaced apart by the same elastomer. The calendering and spacing elastomer employed for the cords adjacent to the beads is the same as the calendering elastomer employed for the cords adjacent to the tread.

Jan. 9, 1973 United States Patent 1191 Montagne [56] References Cited UNITED STATES PATENTS il/i948 [54] ELASTOMERS ASSOCIATED WITH mm m mm S t n m e s 6 b m w u he V t ua -lOr. CFBT 6 6 9 l 2 1 Jean Bernard Montague, Cebazat, 3 172 445 3 9 5 France 3,292,681

[73] Assignee: Compagnie Generale Des Etablisse- Primary Examiner Drayton E- Hoffman melms Michelin I mison sociaie Attorney-Brumbaugh, Graves, Donohue & Raymond Michelin & Cie, Clermont-Ferrand (Puy-de-Dome), France 1970 A radial pneumatic tire comprises at least one carcass 21 Appl. No.: 99,371

[22] Filed:

ply formed of cords. Adjacent to the the tread, the

cords are calendered in an elastomer of a first grade I and spaced apart from one another by an elastomer of Foreign Application Priority Data a second grade. Adjacent to the tire beads, the cords Dec. 23, 1969 France...............................

are calendered in and spaced apart by the same elastomer. The calendering and spacing elastomer employed for the cords adjacent to the heads is the same as the calendering elastomer employed for the cords adjacent to the tread.

C6 505 63 9 7 Ms M s 5 4 l .v n 3 2 5 "I 4 Claims, 3 Drawing Figures PATENTEUJAN 9 197a llvwwxllf INVENTOR. v

JEAN BERNARD MONTAM M y m m m BY I MIMI,

his ATTORNEYS ELASTOMERS ASSOCIATED WITH CORDS OF RADIAL TIRES AT POINTS CLOSE TO AND REMOVED FROM BEADS BACKGROUND OF THE INVENTION This invention relates to radial-carcass pneumatic tires and, more particularly, to a novel and highly-effective radial pneumatic tire having an improved selection of elastomers associated with the radial cords.

In a tire of this type, the carcass comprises one or more layers of cords arranged in radial planes of the tire. Each layer thus consists of parallel or approximately parallel cords embedded in a layer of bonding elastomer such as rubber that adheres to the cords and fills the spaces between adjacent cords. The connecting layer comes from two thin sheets of rubber between high modulus and they are spaced apart from one which the cords have been placed in the form of a sandwich and which have been sealed to each other during the manufacture of the tire. In current industrial practice, the same grade of connecting rubber is used for the different plies of the carcass of a tire and in different regions ofa given ply.

In certain radial-carcass tires, especially tires having a carcass with very elastic cords, certain defects appear. For example, separation of the carcass cords at the end of the folded-back portion of the carcass plies may be noticed in the beads or in the regions of the sidewalls adjacent to the beads. This is true particularly in the case of the carcass ply that extends farthest up in the sidewall after passing around the steel bead wire.

In many cases also one may observe a tearing of the bonding rubber between cords, along radial lines in the upper region of the sidewall, that is to say, in the region of the sidewall between the tread and the middle of the sidewall. Either or both defects may occur, depending on the modulus of elasticity of the selected bonding I rubber.

SUMMARY OF THE INVENTION An object of the present invention is to remedy the problems of conventional radial tires outlined above and, in particular, to provide a tire having a radial carcass that resists both separation of the carcass cords from the surrounding rubber between the middle of the sidewall and the bead wire and tearing of the bonding rubber between the cords in the upper region of the sidewall.

The foregoing and other objects are attained in accordance with the invention by the provision of a tire with a radial carcass comprising at least one layer of radial cords extending in the sidewalls and around the bead wires. The portions of the cords folded back around the bead wires rise in the direction of the sidewalls and terminate at some distance from the bead wires. In accordance with the invention, the cords are (a) in a region of the sidewalls close to the tread, calendered in or surrounded individually by a first grade of an elastomer such as rubber but spaced apart from one another by a second grade of elastomer such as rubber and (b), in a region of the sidewalls close to the bead wire, surrounded individually and spaced apart from one another by the same grade of rubber or other elastomer.

In an embodiment of the invention applicable especially to radial-carcass tires having cords of relatively elastic material, the cords are calendered in or are suranother by a filling rubber that is of relatively low modulus in the upper region of the sidewalls (i.e., in the region adjacent to the tread) and of relatively high modulus in the lower region of the sidewalls (i.e., in the region adjacent to the beads). In the lower region the coating rubber and filling'rubber are of the same grade or quality. I I

The expression modulus in the present context relates to the mechanical behavior of rubber under the conditions of use as a tire. It designates either the dynamic modulus or the static modulus at frequencies, temperatures and types and amplitudes of deformation customary in a tire. However, the static modulus of elasticity at percent elongation and at a temperature of 20C is sufficient in general to characterize in practice the mechanical behavior of a mix; as a matter of fact, no rubbers are known having clearly different mechanical properties which-do not also have substantially different moduli of elasticity at 100 percent elongationat 20C.

A method in accordance with the invention for obtaining a tire as disclosed herein comprises the steps of arranging radially within a ply of cords rolled in a rubber of the first grade a layer of rubber of a second grade and then, upon vulcanizing the tire, exerting a tension on the carcass cords.

In the case of a carcass of cords of material such as polyamides or polyesters, the contraction of the cords at the vulcanizationtemperature is sufficient to place these cords under tension and to cause, in the region remote from the bead wires, as a result of the shortening of the cords, the movement of the cords towards the inside of the tire, partially carrying along-their surrounding rubber, as well as their penetration into the layer of rubber of different quality.

The filling rubber for the cords of the carcass ply in question may itself be the rubber surrounding the individual cords of another carcass ply.

BRIEF DESCRIPTION OF THE DRAWING the line 22 of FIG. I, and looking in the direction of the arrows; and

FIG. 3 is a fragmentary View on the scale of FIG. 2 I

along the line 33 of FIG. 1 and looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows in radial section a tire 10 of size 10.00-20, that is to say, a tire of a rated load of about 2.5 tons.

This tire has a radial carcass l1 composed of three plies 12, I3 and 14 of. polyamide compositecords 1680/3. Each composite cord'is composed of three individual cords of 1680 denier each. The carcass is anchored around two bead wires 15, each ply being folded back and extending in the direction of the sidewall. The tire comprises furthermore a top reinforcement composed of plies l6, l7, l8 and 19 of steel cords, reinforcing the tread 20.

FIGS. 2 and 3 show the sidewalls 22 in cross section perpendicular to the carcass cords, FIG. 2 being a sec- V tion in the upper region, that is to say, at a slight distance from the tread, and FIG. 3 being a section in the lower region, that is to say, in the vicinity of the end of the folded-back portion 25 of the carcass ply 14 rising farthest in the sidewall. FIGS. 2 and 3 show what can actually be observed on a physical tire section which has been'previously ground on the section surface and which is examined in grazing light, that is to say, under conditions which show the different grades of rubber. For the sake of greater clarity, the distances between cords have been somewhat exaggerated.

FIG. 2 shows in succession a layer of rubber 31 forming ,the inner covering of the tire, a layer of rubber 32 embedding the cords of the plies l2 and 13 and extending between the cords of the ply 14, so that the cords of the ply 14 are spaced apart from one another, a layer of rubber 33 individually surrounding the cords of the ply 14, and a layer of sidewall rubber 34.

in accordance with the invention, the cords of the ply 14 are well surrounded individually by a coating or calendering rubber 33'which is of different grade or quality from the filling rubber 32 by which the cords of the ply 14 are spaced apart from one another. The rubber 32 that is inserted between the cords of the ply 14 is the calendering or coating rubber of the cords of plies l2 and 13.

In FIG.v 3 it can be seen that the cords of the ply- 14, including the folded-back portion 25, are arranged in the rubber 33 in the same manner as the cords of the plies l2 and 13 are arranged in the rubber 32.

The arrangement of the carcass cords with respect to the different connecting rubbers isduefirst of all to the fact that the cords of the two inner plies 12 and 13 have been calendered in a rubber 32 'of different quality from the calendering rubber 33 of the cords of the outer ply l4. In one embodiment of the invention, therubber '32 has a modulus of elasticity at 100 percent elongation of 1 l g/mm and a dynamic shear modulus portion 25. This separation occurs at the end of a number of miles which varies in a proportion of l to 5 or 10 depending on the structure of the folded-back portion of the carcass, as set forth in my copending patent application Ser. No. 99,370, for Bead Area Carcass Cord Arrangement for Radial Tires, filed concurrently herewith.

. If the plies l2 and 13 are calendered in a rubberof relatively low modulus and the ply 14 in a rubber of relatively high modulus, one eliminates both the tears in the upper region and the separations of plies in the lower region even after traveling for very many miles, subject to selecting the most favorable structure for the folded-back portion of the carcass.

' Many modifications of the preferred embodiments of the invention disclosed herein will readily occur to those skilled in the art. For example, the invention is not dependent on any particular selection of material for the carcass cords, although the advantages it produces may be greater or lesser, depending on the nature of the material. Also, the present invention and that disclosed in my copending application Ser. No. 99,370, for Bead Area Carcass Cord Arrangement for Radial Tires", filed concurrently herewith, may be embodied in the construction of the same tire. Accordingly, the invention is to be construed as including all the embodiments thereof within the scope of the appended claims.

1. A radial pneumatic tire comprising a pair of beads, a pair of bead wires respectively reinforcing said beads, a pair of sidewalls respectively joined to said beads, a tread extending between said sidewalls, and at least one carcass ply,.said carcass ply being formed of cords, an

' elastomer of a first grade calendering said cords and at a frequency of IO cps of 10.0 X 10 Nlm while the rubber 33 has a modulus of elasticity of 400 g/mm at 100 percent elongation and a dynamic shear modulus of 102 l0? N/m at a frequency of 10 cps. Upon the vulcanization of the, tire, the polyamide cords contract at a temperature of about 150C, and a displacement of the cords towards the inside of the tire takes place. The displacement is particularly marked in the upper region ofthe tire. v

Comparative tests have shown the following results: a. If the three plies 12, 13, and 14 are calendered in the same rubber of high modulus, tears of the rubber between cords in the upper region of the tire appear after relatively few miles of travel. b. If the three plies 12,13 and 14 are calendered in the same rubber of low modulus, one avoids the tears of the rubber between cords in the upper region but notes a separation of the cords of the ply 14 at the level of the end 26 of the folded-back having on at least one side thereof a wavy surface, said surface defining waves of which thelength equals the center-to-center distance between adjacent cords and of which'the amplitude in the region of the sidewalls adjacent to the tread is relatively high and in the region of the sidewalls adjacent to the beads is relatively low, and an elastomer of a second grade having a surface in contact with and complemental to said wavy surface,

said elastomer of a secondgrade spacing said cords apart from one another adjacent to said tread. 2. A tire according to claim l wherein said elastomer of a first grade is a relatively high-modulus rubber and said elastomer of a second grade is a relatively low modulus rubber. V I

3. A radial pneumatic tire comprising a pair of beads, a pair of bead wires respectively reinforcing said beads, a pair of sidewallsrespectively joinedto said beads, a tread extending between said sidewalls, and, at least one carcass ply, said carcass ply being formed of cords, a tread-adjacent elastomer of a first grade calendering said cords adjacent to said tread, a tread-adjacent elastomer of a second grade spacing said cords apart from one another adjacent to said tread, and a bead-adjacent elastomer of a single grade calendering said cords and spacing said cords apart from one another adjacent to said beads, further comprising at least one additional carcass ply, said additional carcass ply being formed of cords, the cords of said one ply being calendered in said elastomer of a first grade and the cords of 4 said additional ply being calendered in said elastomer of a second grade.

4. A tire according to claim 3 wherein the cords of said -one.ply are of a material that contracts when heated. 5 

1. A radial pneumatic tire comprising a pair of beads, a pair of bead wires respectively reinforcing said beads, a pair of sidewalls respectively joined to said beads, a tread extending between said sidewalls, and at least one carcass ply, said carcass ply being formed of cords, an elastomer of a first grade calendering said cords and having on at least one side thereof a wavy surface, said surface defining waves of which the length equals the center-to-center distance between adjacent cords and of which the amplitude in the region of the sidewalls adjacent to the tread is relatively high and in the region of the sidewalls adjacent to the beads is relatively low, and an elastomer of a second grade having a surface in contact with and complemental to said wavy surface, said elastomer of a second grade spacing said cords apart from one another adjacent to said tread.
 2. A tire according to claim 1 wherein said elastomer of a first grade is a relatively high-modulus rubber and said elastomer of a second grade is a relatively low-modulus rubber.
 3. A radial pneumatic tire comprising a pair of beads, a pair of bead wires respectively reinforcing said beads, a pair of sidewalls respectively joined to said beads, a tread extending between said sidewalls, and at least one carcass ply, said carcass ply being formed of cords, a tread-adjacent elastomer of a first grade calendering said cords adjacent to said tread, a tread-adjacent elastomer of a second grade spacing said cords apart from one another adjacent to said tread, and a bead-adjacent elastomer of a single grade calendering said cords and spacing said cords apart from one another adjacent to said beads, further comprising at least one additional carcass ply, said additional carcass ply being formed of cords, the cords of said one ply being calendered in said elastomer of a first grade and the cords of said additional ply being calendered in said elastomer of a second grade.
 4. A tire according to claim 3 wherein the cords of said one ply are of a material that contracts when heated. 